% calculate the length of calf from human data
% xpt1,ypt1 are the position ankle_avg
% xpt2, ypt2 are the position of knee
function ret = cal_Lc(xpt1,ypt1,xpt2,ypt2)
  sum_length = 0;
  for i = 1:length(xpt1)
      sum_length = sum_length+sqrt((xpt1(i)-xpt2(i))^2+(ypt1(i)-ypt2(i))^2);
  end
  ret = sum_length/length(xpt1);
end